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Convenient fixture for testing infrared detector integrated circuits, such as those used in surveying sensors, optical communications, receivers, optical power meters, and noncontacting thermometers. Includes electrical connections for 42-pin dual-in-line package (DIP), thermal connection to cryogenic probe, and optical filter. Using fixture, electrical and optical properties of detector measured at 4 K.
Researchers describe the most important radiation response issues for infrared detectors. In general, the two key degradation mechanisms in infrared detectors are the noise produced by exposure to a flux of ionizing particles (e.g.; trapped electronics and protons, debris gammas and electrons, radioactive decay of neutron-activated materials) and permanent damage produced by exposure to total dose. Total-dose-induced damage is most often the result of charge trapping in insulators or at interfaces. Exposure to short pulses of ionization (e.g.; prompt x rays or gammas, delayed gammas) will cause detector upset. However, this upset is not important to a sensor unless the recovery time is too long. A few detector technologies are vulnerable to neutron-induced displacement damage, but fortunately most are not. Researchers compare the responses of the new technologies with those of the mainstream technologies of PV HgCdTe and IBC Si:As. One important reason for this comparison is to note where some of the newer technologies have the potential to provide significantly improved radiation hardness compared with that of the mainstream technologies, and thus to provide greater motivation for the pursuit of these technologies.
This viewgraph presentation reviews the modeling of Quantum Well Infrared Detectors (QWIP) and Quantum Dot Infrared Detectors (QDIP) in the development of Focal Plane Arrays (FPA). The QWIP Detector being developed is a dual band detector. It is capable of running on two bands Long-Wave Infrared (LWIR) and Medium Wavelength Infrared (MWIR). The same large-format dual-band FPA technology can be applied to Quantum Dot Infrared Photodetector (QDIP) with no modification, once QDIP exceeds QWIP in single device performance. Details of the devices are reviewed.
Long wavelength infrared detection is achieved by a detector made with layers of quantum well material bounded on each side by barrier material to form paired quantum wells, each quantum well having a single energy level. The width and depth of the paired quantum wells, and the spacing therebetween, are selected to split the single energy level with an upper energy level near the top of the energy wells. The spacing is selected for splitting the single energy level into two energy levels with a difference between levels sufficiently small for detection of infrared radiation of a desired wavelength.
Long wavelength Si 1-X Ge X /Si heterojunction internal photoemission (HIP) infrared detectors have been successfully demonstrated utilizing the growth of degenerately boron doped Si 1-X Ge X layers on Si. Recently, Si 0.7 GE 0.3 /SI HIP detectors with either a Si 1-X Ge X single layer or a Si 1-X Ge X /Si multilayer have been demonstrated with cutoff wavelengths out to 23 µm. Near-ideal thermionic emission dark current characteristics were measured and the electrical potential barriers were determined by the Richardson plot. A photoresponse model, similar to the modified Fowler Equation has been developed for the Si 1-X Ge X /Si heterojunction internal photoemission infrared detector at wavelengths corresponding to photon energies less than the Fermi energy. The optical potential barriers, the corresponding cutoff wavelengths, and the emission coefficients, C 1 , for the HIP detectors have been determined from the measured spectral responses using the photoresponse model. Similar optical and thermal potential barriers were obtained.
Proposed detector of infrared photons based on photon-assisted, resonant quantum-mechanical tunneling between adjacent energy wells in its semiconductor structure. Wavelength adjusted by changing applied voltage. Device contains alternating layers of different seminconductors which form double-quantum-well electron-energy structure. Tunable-quantum-well detectors made on single chip constitutes line imager. Many such devices stacked to form two-dimensional imaging device. Signal-processing circuitry integrated into chip at its lower end. Potential barriers and wells produced by alternating layers of different semiconductor materials. Steepness of slope proportional to applied electric field. Electric field and thicknesses and heights of barriers selected to favor photon-assisted, resonant quantum-mechanical tunneling at chosen photon frequency.
The Diffuse Infrared Background Experiment (DIRBE) is one of three experiments to be carried aboard the Cosmic Background Explorer (COBE) satellite scheduled to be launched by NASA on a Delta rocket in 1989. The DIRBE is a cryogenic absolute photometer operating in a liquid helium dewar at 1.5 K. Photometric stability is a principal requirement for achieving the scientific objectives of this experiment. The Infrared Astronomy Satellite (IRAS), launched in 1983, which used detectors similar to those in DIRBE, revealed substantial changes in detector responsivity following exposure to ionizing radiation encountered on passage through the South Atlantic Anomaly (SAA). Since the COBE will use the same 900 Km sun-synchronous orbit as IRAS, ionizing radiation-induced performance changes in the detectors were a major concern. Here, ionizing radiation tests carried out on all the DIRBE photodetectors are reported. Responsivity changes following exposure to gamma rays, protons, and alpha particle are discussed. The detector performance was monitored following a simulated entire mission life dose. In addition, the response of the detectors to individual particle interactions was measured. The InSb photovoltaic detectors and the Blocked Impurity Band (BIB) detectors revealed no significant change in responsivity following radiation exposure. The Ge:Ga detectors show large effects which were greatly reduced by proper thermal annealing.
The InAs/InAsSb (Gallium-free) type-II strained-layer superlattice (T2SLS) has emerged in recent years as a viable infrared detector material. In particular, mid-wavelength InAs/InAsSb T2SLS focal plane array (FPA) based on the nBn detector architecture exhibits good operating characteristics at 160 K, demonstrating a considerably operating temperature advantage over InSb FPAs. In the long and very long cutoff wavelengths, InAs/InAsSb T2SLS detectors with n-type absorbers are limited in their attainable quantum efficiency (QE) due to shorter hole diffusion lengths and relatively modest absorption coefficients. We have explored long and very long wavelength InAs/InAsSb T2SLS complementary barrier infrared detectors (CBIRDs) that contain p-type absorber layers in order to take advantage of the longer electron diffusion length for QE enhancement. We also discuss recent development of the InAs/InAsSb T2SLS infrared detectors at the Jet Propulsion Laboratory for NASA Earth Science applications, including long-wavelength infrared FPAs for land imaging, and mid-wavelength infrared FPAs for CubeSat hyperspectral imaging.
The paper describes the design, fabrication, and characteristics of a novel infrared detector based on the principle of Golay's (1947) pneumatic infrared detector, which uses the expansion of a gas to detect infrared radiation. The present detector is constructed entirely from micromachined silicon and uses an electron tunneling displacement transducer for the detection of gas expansion. The sensitivity of the new detector is competitive with the best commercial pyroelectric sensors and can be readily improved by an order of magnitude through the use of an optimized transducer.
There exists a considerable interest in the broadband detectors for CLARREO Mission, which can be used to detect CO2, O3, H2O, CH4, and other gases. Detection of these species is critical for understanding the Earth?s atmosphere, atmospheric chemistry, and systemic force driving climatic changes. Discussions are focused on current and the most recent detectors developed in SWIR-to-Far infrared range for CLARREO space-based instrument to measure the above-mentioned species. These detector components will make instruments designed for these critical detections more efficient while reducing complexity and associated electronics and weight. We will review the on-going detector technology efforts in the SWIR to Far-IR regions at different organizations in this study.
The CubeSat Infrared Atmospheric Sounder (CIRAS) is a remote sensing instrument under development for thedemonstration and technology maturation of hyperspectral infrared sounding in a 6U CubeSat. The CIRASinstrument utilizes a 2D Focal Plane Array (FPA) of High Operating Temperature-Barrier Infrared Detectors(HOT-BIRD). The HOT-BIRD material provides improved uniformity, higher allowable operating temperatures,and lower 1/f noise. The performance of the HOT-BIRD FPA was tested inside a Integrated Dewarand Cryocooler Assembly (IDCA), allowing the operating temperature of the FPA to reach low temperatures.Experimentation involved using an external Blackbody Calibrator Target (BCT) to generate numerous imagesof the BCT object at varying scene temperatures. The data acquired was compared to a radiometric model tocharacterize the responsivity of the detectors. In addition, a solid angle correction was developed to improve theaccuracy of the modeling. Real and synthetic images are presented in the comparative analysis to validate theexpected responsivity of the detectors through calculation of the quantum efficency.
We explore long wavelength InAs/InAsSb superlattice complementary barrier infrared detectors that contain p-type absorber layers for quantum efficiency enhancement. We also discuss type-II superlattice infrared detector technology for NASA Earth Science applications, including LWIR FPAs for land imaging, and MWIR FPAs for CubeSat hyperspectral imaging.
Near-infrared array detectors, like the James Webb Space Telescope (JWST) NIRSpec's Teledyne's H2RGs, often provide reference pixels and a reference output. These are used to remove correlated noise. Improved reference sampling and subtraction (IRS(exp 2)) is a statistical technique for using this reference information optimally in a leastsquares sense. Compared with the traditional H2RG readout, IRS(exp 2) uses a different clocking pattern to interleave many more reference pixels into the data than is otherwise possible. Compared with standard reference correction techniques, IRS(exp 2) subtracts the reference pixels and reference output using a statistically optimized set of frequency dependent weights. The benefits include somewhat lower noise variance and much less obvious correlated noise. NIRSpec's IRS(exp 2) images are cosmetically clean, with less 1/f banding than in traditional data from the same system. This article describes the IRS(exp 2) clocking pattern and presents the equations needed to use IRS(exp 2) in systems other than NIRSpec. For NIRSpec, applying these equations is already an option in the calibration pipeline. As an aid to instrument builders, we provide our prototype IRS(exp 2) calibration software and sample JWST NIRSpec data. The same techniques are applicable to other detector systems, including those based on Teledyne's H4RG arrays. The H4RG's interleaved reference pixel readout mode is effectively one IRS(exp 2) pattern.
Mid-infrared detector arrays operating from 2.8 to 20 μm are baselined in the design of the Origins Space Telescope Mid-Infrared Spectrometer Instrument. This instrument is designed to detect and measure the spectral signatures of gases of biogenic origin in the atmospheres of exoplanets as they transit their host stars. In order to make these detections, the detector array’s pixels need to have high-signal stability when exposed to a constant flux in multiple time-series integration over a typical transit time of a few hours. With the use of a densified pupil spectrometer design, pointing effects can be mitigated because pointing variations do not displace spectra on the detector and each wavelength of light is averaged over a large number of pixels, giving good spectrophotometric stabilities. The current state-of-the-art detector arrays do not achieve these stabilities, although with a feasible development program this level of performance should be achievable. Three detector technologies are under consideration for this development, HgCdTe arrays, Si:As impurity band conduction arrays, and transition edge super-conductor bolometer arrays. We primarily treat the HgCdTe technology development, but also introduce the paths forward for the other two technologies. After a few years-long investigative programs, a down-select will be undertaken to select the flight technology.
It is customary to make infrared (IR) detectors in the long wavelength range (8-20 (micro)m) by utilizing the interband transition which promotes an electron across the band gap (E(sub g)) from the valence band to the conduction. These photo-electrons can be collected efficiently, thereby producing a photocurrent in the external circuit.
The Jet Propulsion Laboratory has a long history in the development and application of infrared detector technology for the exploration of our planetary system. We will describe some recent applications of IR detector technology at JPL for ground based astronomy, the Earth Observing System, the Cassini Mission to Saturn, and the other proposed planetary missions. The infrared detector technologies to be discussed include single element, multiplexed linear and staring arrays, using a wide variety of infrared sensing materials including InSb, InGaAs, HgCdTe (PV and PC) and SiAs.
A d.c.-coupled transimpedance amplifier/pulse suppression circuit designed to remove charged-particle-induced noise from infrared detectors is described. Noise spikes produced by single particle events are large and have short rise times, and can degrade the performance of an infrared detector in moderate radiation environments. The use of the suppression circuit improves the signal-to-noise ratio by a factor of 1.6:1, which corresponds to a reduction in required observing time by a factor of about 2.6.
Researchers fabricated and characterized several AlGaAs/GaAs multiple quantum well infrared detectors to evaluate the ultimate performance of these devices for low infrared background applications. The detectors were designed to have a single bound state in the quantum well and the first excited state in the continuum above the AlGaAs conduction band edge. The difference in energy between the two levels, as determined by the quantum well width and aluminum mole fraction in the barrier, was chosen such that peak absorption would occur near 8 microns. The initial structures studied comprised 50 periods with 40 A well widths and 300 A Al(0.28)Ga(0.72)As barriers. The performance of these detectors are summarized. To better interpret these results and design optimized detectors, researchers modeled both the detector noise and tunneling currents. The noise model correctly predicts that multiple quantum well detectors will, indeed, exhibit noise lower than full shot noise. The tunneling current model predicts the dark current versus bias for any choice of design parameters in a multiple quantum well detector. This model predicts a substantially reduced dark current (x 10(exp 04)) for samples with 400 A barriers. To evaluate structures with thicker barriers, researchers fabricated and characterized detectors with 400 A and 500 A barriers; a comparison of detector dark currents is shown. These results are consistent with the predictions of the dark current model.